In the '70s, Keith Jarrett worked with two ensembles that came to be known as the American Quartet and the European Quartet. The latter group included a pair of Norwegians—saxophonist Jan Garbarek and drummer Jon Christensen—and Swedish bassist Palle Danielsson. 2012’s Sleeper, the fifth album by the European Quartet, presents never-before-released recordings from a 1979 live show in Tokyo. Fans won't be disappointed: the exacting unit is in top form, and the sound is excellent. “Personal Mountains” kicks things off, and the band immediately engages: Christensen creates a rhythmic whirlwind, Danielsson drives hard, and Jarrett’s and Garbarek’s solos are supercharged. There is one exciting passage, without piano or sax, where drums, percussion, and bass are absolutely on fire. “So Tender” brings out the quartet’s lyrical side, but the music still bristles with energy. “Oasis,” which opens with a mysterious flute-and-percussion section and closes with a rollicking free jazz workout, takes the listener on quite a journey. The subtly pop-inflected “New Dance” wraps up things on an upbeat note.